William s



(No Model.)

W. S. P. DILLON.

TAP.AND DIE.

Patented Apr. 8, 1890.

1 u M! F M UNITED STATES PATENT rrrcn.

lVILLIAllL S. F. DILLON, OF LIMA, OHIO, ASSIGNOR OF ONE-HALF TO GEORGE HALL, OF SAME PLACE.

TAP AND DIE.

SPECIFICATION forming part of Letters Patent No. 425,372, dated April 8, 1890.

Application filed December 20, 1889. Serial No. 334,351. (llo model.)

To all whom it may concern.-

Be it known that I, W'ILLIAM S. F. DILLON, a citizen of Jamaica, est Indies, residing at Lima, in the county of Allen and State of Ohio, have invented certain new and useful Improvements in Cutting-Edges for Taps and Dies; and I do declare the following to be a full, clean-and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, and to letters of reference marked thereon, which form a part of this specification.

This invention relates to improvements in the cutting-edges of taps and dies, the object being to so construct the same as to lessen the liability which they have of becoming broken and dulled.

In describing the invention I will confine myself to the same as applied to a tap, but which may obviously be applied to any tool with which such edges are used.

In the tap in ordinary use the edge of the threads which first begins to cut is liable to be broken or crushed, owing to the fact that the entrance of the edge into the metal is sudden and abrupt, causing great strain to be brought upon it, and, not being well backed by metal, produces the result mentioned.

My invention further relates to the novel construction and combination of parts hereinafter described, illustrated in the accoming drawings, and pointed out in the claims hereto appended.

In the accompanying drawings, in which similar letters of reference designate corresponding parts, Figure 'l is a plan view of a tap embodying the invention. Fig. 2 is a crosssection of the same. Fig. 3 is an enlarged detail of the cutting-edges. Fig. dis a modification showing a different means of forming the cutting-edges. Fig. 5 is a plan view of a die embodying the invention. Fig. 6 is a sectional view of the same.

In making my tap I take the ordinary tap A, ungrooved, and out in it the spiral grooves B B in the direction opposite to that taken by the threads. If it be a right-hand thread, I out the grooves from right to left; if a lefthand thread, I cut from left to right. The pitch of the groove is very steep, not encircling a tap of ordinary length but for a short distance. Thesegrooves passing around the tap form cutting-edges where they intersect the threads. Edges formed in this manner will have the upper part a projecting beyond the lower part 1). Consequently the upper part will engage with the metal to be cut first. The pressure exerted on this part of the edge will be toward the upper end of the tap. I'Vhen the edges are so formed, they will have a firm foundation or backing of metal 0 to withstand the pressure brought to bear on them. This backing slopes backward toward the end of the tap, forming a foundation for the lower part b. The two parts a and 1) form a cutting-edge, which will gradually enter the metal to be out, and, being well backed, be secured against the liability of being broken or crushed. This I have found to be the best and most practicable way of making the edge; but it may be made by taking an ordinary tap (see Fig. 4) having straight grooves I3 13 and out each edge separately by removing a portion e of the thread. This way would be long, tedious, and costly, the spiral groove being much easier to make, and hence to be preferred. In those taps which are spirally grooved the grooves pass around the tap in the same general direction taken by the threads, but in no case have I found them to pass in a direction opposite to that taken by the threads. Nhen the grooves pass around the tap in the same general direction as the threads, the lower portion of the cutting-edge is so form ed as to be the first to engage with the metal to be out. The pressure being in the direction of the end of the tap, would tend to crush or break oif the frail lower' edge. This is also the case when the grooves are straight. I have also found that the edges in the ordinary dies do not free themselves of the shavings, as those constructed in the manner described.

Spiral grooves having been made on taps before, I do not, therefore, broadly claim such a construction; but

lVhat I do claim, and desire to secure by Letters Patent, is

1. As an improvement in taps and dies, a v by the threads, substantially as and for the 10 cutting-edge so formed that the upper part of the same Will project beyond the lower, substantially as shown and described.

2. As an improvement in taps and dies, a cutting-edge formed by the intersection of the threads of the tap and of a spiral groove partly encircling the same, passing around the tap in a direction opposite to that taken purpose specified.

In testimony whereof I affix my signature in presence of two Witnesses.

WILLIAM S. F. DILLON. 

